1. Field of the Invention
The present invention generally relates to the field of clocks and, more specifically to a frequency detecting and converting apparatus for automatically detecting the frequency of an input clock signal and then dividing the frequency to a desired frequency required for an integrated circuit (IC).
2. Description of the Related Art
Generally, main operating frequency of IC is fixed. For example, a universal serial bus (USB) controller normally operates at 6 MHz (low speed) or 48 MHz (high speed). Thus, a clock frequency provided to the USB controller is generated by an oscillator having a frequency of 6 MHz or 48 MHz. Instead, an output clock frequency of an oscillator having a frequency of 6 MHz or 12 MHz is multiplied with a phase-locked-loop up to a resultant clock frequency of 48 MHz.
Oscillators on the market usually are restricted to different sizes, selling prices and popularity with respect to different frequencies. If an IC is limited to use an oscillator having a fixed frequency, the flexibility in production and application may lessen as the oscillator is in a short supply or has a big size.